Winter 2016 | .colorado.edu

From BEC to Forever p.1 JILA &

Smiling faces at JILAday, December 8, 2015. Credit: Steve Burrows, JILA

JILA Light & Matter is published quarterly by the Scientific Communications Office at JILA, a joint in- stitute of the University of Colorado Boulder and the National Institute of Standards and Technology.

The editors do their best to track down recently published journal articles and great research photos and graphics. If you have an image or a recent paper that you’d like to see featured, contact us at: [email protected].

Please check out this issue of JILA Light & Matter online at https://jila.colorado.edu/publications/jila/ light-matter.

Kristin Conrad, Project Manager, Design & Production Julie Phillips, Science Writer Steven Burrows, Art & Photography Gwen Dickinson, Editor Winter 2016 | jila.colorado.edu

Stories

From BEC to Breathing Forever 1

Turbulence: An Unexpected Journey 3

The Guiding Light 5

A Thousand Splendid Pairs 9

Born of Frustration 13

The Land of Enhancement: AFM 15

Natural Born Entanglers 17

Dancing to the Quantum Drum Song 19 Features NIST Boulder Lab Building Renamed for

Katharine Blodgett Gebbie 7 JILA Puzzle 11 In the News 21 How Did They Get Here? 23 Atomic & Molecular

From BEC to Forever The storied history of JILA’s Top Trap t took Eric Cornell three years to build JILA’s spherical Top Trap with his own two hands in the lab. The innovative trap relied primarily on magnetic Ifields and gravity to trap ultracold atoms. In 1995, Cornell and his colleagues used the Top Trap to make the world’s first Bose-Einstein condensate (BEC), an achievement that earned Cornell and the Nobel Prize in 2001.

The Nobel-Prize-winning creation of BEC had been Although today revere Boltzmann as a a race to the finish line, as labs all over the world had giant in the field of physics, he was vehemently also been attempting to be the first to validate the attacked when he published the transport equa- 70-year-old prediction of BEC by Satyendra Nath tion in 1876. For starters, Boltzmann assumed that Bose and . The innovative Top Trap matter was made of atoms, an idea that was vig- was the key to Wieman and Cornell’s great achieve- orously disputed at the time by many scientists ment. Afterwards, Cornell, Wieman, and their col- who claimed energy was at the root of the physical leagues conducted a host of Top-Trap experiments, world. With respect to the special case showing that publishing 20 significant papers on the physics of it was possible for a physical process to continue ultracold atoms over the next two decades. forever without damping, or stopping completely, “everyone” knew that was crazy. If something starts By the end of that 20–year period of discovery, moving, it slows down or cools down. Eggs break, however, the now much older (and more com- for heaven’s sake, and they don’t reform into eggs. plicated) Top Trap was wearing out. It was time That’s just the way the world works! to think about one last experiment. Only one of Cornell’s graduate students, Dan Lobser, knew Boltzmann’s controversial idea was that damping how to operate the complicated apparatus. So happens when you put lots of atoms together, with Cornell and Lobser enlisted additional help from just one or two exceptions. This idea was heresy to student assistant Andrew Barentine and Fellow the scientific establishment of his time. It was also , who had previously worked right. with Lobser. Even though physicists today believed the special Cornell and Lewandowski decided upon a fitting case is correct because the rest of the trans- final experiment for the Top Trap: a test of a special port equation has been validated, Cornell and case of Boltzmann’s transport equation that had Lewandowski decided to prove it. The Top Trap never been proved. This part of Boltzmann’s theory was the perfect instrument to use. predicted that, once set in motion, a cloud of atoms in a perfectly spherical trap would breathe, The researchers placed an ultracold cloud of ru- or oscillate, forever. It was a perfect experiment for bidium atoms in the Top Trap and started the the Top Trap despite being somewhat of an histori- cloud oscillating. The cloud oscillated in and out cal oddity. in what’s known as a “monopole breathe.” While it

1 Winter 2016 , JILA Light & Matter atoms “breathing” endlessly in the Top Trap. Credit: The Lewandowski and Cornell groups and Steve Burrows, JILA was “breathing,” the cloud changed in volume by about 30%. Most importantly, the breathing continued for a very long time—long enough to vindicate Boltzmann.

When the researchers finished taking the data for the experiment, they disassembled the Top Trap. While this was happening, Eric Cornell walked out of the lab where he’d started an amazing scientific journey at JILA 25 years earlier. It was hard to watch an “old friend” disappear, though perhaps not quite as hard as it had been for Boltzmann to be dismissed and reviled for his stunning insights into the nature of the physical world.

D. S. Lobser, A. E. S. Barentine, E. A. Cornell, and H. J. Lewandowski, Nature Physics, 11 1009–1012 (2015).

Winter 2016 . JILA Light & Matter 2 Astrophysics

Artist’s impression of a young star surrounded by an accretion disk. This system is similar to the HD 163296 system theoretically analyzed by Phil Armitage and Jacob Simon before being observed by ALMA. Credit: ALMA(ESO/NAOJ/NRAO)

Turbulence: An Unexpected Journey

ellow Phil Armitage and his collaborator Jake Simon of the Southwest Research Institute re- cently conducted a theoretical study of turbulence in the outer reaches of an accretion disk Faround HD 163296, a nearby young star. Meanwhile, the Atacama Large Millimeter/submil- limeter Array (ALMA) in northern Chile observed the same accretion disk. There were intriguing and un- expected differences between what the theory predicted and what the observation revealed. As a result, theorists may need to rethink their understanding of the behavior of an accretion disk at great distances from the central star.

3 Winter 2016 , JILA Light & Matter Astrophysics

ALMA’s 16-antenna Atacama Compact Array, or ACA, enhances imaging fidelity for extended astronomical sources. Credit: ALMA(ESO/NAOJ/NRAO)

“The outer disks we’re interested in should have Sun to the Earth) flowing in and accreting onto the some sort of turbulence, some significant gas star. So something—quite likely turbulence—is remov- motion that departs from the simple rotation (of ing the angular momentum in the inner disk regions. the disk),” said Simon. Simon explained that some- thing has to remove the disk’s angular momentum However, at 100 AU (two and a half times the dis- to allow the gas to move towards the central star. tance from the Sun to Pluto), there is no reason, Turbulence was, and still is, the primary explanation in principle, that the gas has to be turbulent or for how this happens. However, ALMA detected no flowing inward at all. The gas could just be sitting clear evidence of turbulence in the outer disk. there orbiting the young star until it eventually gets blown away because of heating by x-rays or ultra- “ALMA is a revolutionary instrument,” explained violet radiation from the star. Armitage. He said people had predicted that ALMA would overturn some theoretical ideas, but he and “The new observation is interesting, exciting, and Simon hadn’t expected it to be their ideas. Even more mysterious now than before.” said Armitage. so, he and Simon are excited that the new obser- “The issue here is not the precision of the mea- vations are giving them the opportunity to revisit surements, which is extremely good, but how their theory to account for the new observation. those measurements are interpreted.” He added And, if this observation holds up with other planet- that there are things in the Universe that may not forming systems, it will be Simon and Armitage’s work in quite the way people currently understand job to figure out exactly what’s going on. them. And, according to Armitage and Simon, this is the sort of mystery that makes it great fun to do Armitage said that there may be a period of con- theoretical astrophysics. fusion on both the observational and theoretical sides before it becomes clear what’s happening Kevin M. Flaherty, A. Meredith Hughes, Katherine A. Rosenfeld, Sean M. in the outer region of the accretion disk of HD Andrews, Eugene Chiang, Jacob B. Simon, Skylar Kerzner, David J. Wilner, The Astrophysical Journal, 813:99 (2015). 163296. An interesting part of this conundrum is that there are observations that clearly show material Jacob B. Simon, A. Meredith Hughes, Kevin M. Flaherty, Xue-Ning Bai, and Philip J. Armitage, The Astrophysical Journal 808:180 (2015). at 1 astronomical unit, or AU (the distance from the

Winter 2016 . JILA Light & Matter 4 When beams of visible light with opposite circular polarizations are crossed in a high-harmonic generation process, an array of harmonics (x-ray beams) is produced at different angles, which allows the harmonics to be easily separated. Right and left circularly polarized x-ray laser beams are produced on opposite sides. Credit: The Kapteyn/Murnane group and Steve Burrows, JILA

5 Winter 2016 , JILA Light & Matter Laser Physics

The Guiding Light Visible provide exquisite control of x-ray light he Kapteyn/Murnane group, with Visiting Fellow Charles Durfee, has figured out how to use visible lasers to control x-ray light! The new method Tnot only preserves the beautiful coherence of laser light, but also makes an array of perfect x-ray laser beams with controlled direction and .

Such pulses may soon be used for observing polarization, and spectrum of light in the x-ray chemical reactions or investigating the electronic region.” motions inside atoms. They are also well suited for studying magnetic materials and chiral molecules The researchers responsible for this breakthrough like proteins or DNA that come in left- and right- include Hickstein, former senior research associate handed versions. Franklin Dollar, research associates Patrik Grychtol and Ronny Knut, former research associate Carlos This new discovery has taken tabletop femtosec- Hernández-Garcia, graduate students Jennifer ond (10–15 s) and attosecond (10–18 s) x-ray bursts Ellis, Dmitriy Zusin, Christian Gentry, Tingting Fan, to a whole new level. The secret to the discovery: and Kevin Dorney, Justin Shaw (NIST), Visiting Research associate Dan Hickstein crossed two Fellow Charles Durfee (Colorado School of Mines), visible laser beams that were circularly polarized in Associate Fellow Agnieszka Jaron-Becker, and opposite directions and sent them through a high- Fellows Andreas Becker, Henry Kapteyn, and harmonic generation (HHG) process. The crossed Margaret Murnane. laser beams entered a gas of argon where the laser field ripped electrons from the noble gas atoms. Visible lasers can now be used to precisely control The laser field then changed direction, smashing x-rays, opening the door to investigating materi- the electrons back into their parent ions and pro- als in ways that were never before possible. In fact, ducing an array of harmonics (soft x-ray beams of the technique is so new that no one yet knows its different wavelengths). limits: The researchers don’t yet know how high in energy they can make the pulses; nor do they The new technique produced different color x-ray know how short a pulse they can generate or how beams that emerged at distinct angles. As a result, it bright it can be. was straightforward to isolate and separate beams of different wavelengths and polarizations. And, “The most dramatic advance here is that we now with this capability came the power to tailor spe- have the ability to steer x-ray light with visible cific x-ray laser beams to individual experiments. lasers,” Murnane said. “To my knowledge, this is the first time anyone has figured out how to steer “All the left circularly polarized beams go in one di- an x-ray beam with visible light. It’s really beautiful rection, and all the right circularly polarized beams light science.” go in the other direction,” said Murnane. “This is quite amazing! Nobody thought you could have The new method promises to be a boon to the so much simultaneous control of the direction, use of x-ray laser beams in scientific (cont. pg. 7)

Winter 2016 , JILA Light & Matter 6 Laser Physics | Honors

experiments because good optics are not avail- NIST Boulder Lab Building able to steer x-ray light. Those that are available Renamed for Katharine are expensive, and they don’t work very well. Plus, Blodgett Gebbie it’s very difficult to design optics that preserve the very short bursts generated by HHG. In contrast, Dr. Katharine Blodgett Gebbie, long-time JILAn and the new-found capability of manipulating x-ray former director of the National Institute of Standards light via the HHG generation process circumvents and Technology’s (NIST’s) Physical Measurement these disadvantages, making it easier to “see” Laboratory, was honored by NIST on December 10. The what’s happening in experiments. most advanced laboratory building at the NIST campus in Boulder, Colorado, was renamed after legendary lab- The nice thing about the new system is that re- oratory director Gebbie. searchers know what’s happening in real time, and, if needed, they can adjust the x-rays with a visible This is the first time a NIST Boulder building has been laser. So far, the researchers have used their new named for a person. Such honors have been rare in HHG x-ray beams to investigate magnetic mate- NIST’s 114-year history across several locations. The rials. Their goal is to refine the new technique to last time a NIST building was named for a staff member create an x-ray spectrometer without using any was in 1962 at the institution’s original headquarters in x-ray optics. Washington, D.C.

Daniel D. Hickstein, Franklin J. Dollar, Patrik Grychtol, Jennifer L. Ellis, Gebbie, currently a NIST senior advisor, is uniquely de- Ronny Knut, Carlos Hernández-García, Dmitriy Zusin, Christian Gentry, serving of such an honor. An astrophysicist by training, Justin M Shaw, Tingting Fan, Kevin M. Dorney, Andreas Becker, Agnieszka she has worked for NIST for more than 45 years. Among Jaron-Becker, Henry C. Kapteyn, Margaret M. Murnane, and Charles G. Durfee, Nature Photonics, 9 743–750 (2015). other positions, she directed two large NIST operating units of several hundred researchers each. Under her leadership, NIST staff won four Nobel Prizes in Physics between 1997 and 2012 as well as two MacArthur Fellowships, a.k.a. “genius grants.”

Gebbie also played leadership roles in founding NIST’s Summer Undergraduate Research Fellowship (SURF) program and the Joint Quantum Institute, and in advo- cating for women and minorities in science.

“This renaming is our small way of saying thank you, Katharine, for all you’ve done for this organization over such a long period of time,” said Under Secretary of Commerce for Standards and Technology and NIST Director Willie E. May. “This gesture will serve as a re- minder for all of us for years to come who Katharine is and was and the remarkable environment that she fos- tered within NIST and the laboratories that she led.”

A quiet and snowy view from JILA while students The renaming was celebrated at a ceremony where were away for the holidays. Gebbie was presented with many tributes—a stand- ing ovation from an overflow crowd of about 200 staff

7 Winter 2016 , JILA Light & Matter Honors

and guests; a letter from Colorado Governor John Hickenlooper; and an American flag once flown over the U.S. Capitol in Washington, D.C., provided by local Congressman Jared Polis.

All four NIST Nobel laureates spoke glowingly and told personal anecdotes about Gebbie’s quest for ex- cellence, as well as her loyalty and nurturing support that encouraged them to succeed—and remain at NIST throughout their careers.

“Katharine—we revere you, we are in awe of you, and we love you,” NIST Fellow and 1997 Nobel laureate William Phillips said.

A typical Gebbie response to such accolades is: “Of course, all I did was hire and retain talented scientists and support staff.” (She was unable to attend the cer- emony in person.)

The renamed laboratory building, first dedicated in 2012, tightly controls environmental conditions such as vibration and temperature, as required for cutting- edge research and measurements with world-leading Katharine Blodgett Gebbie was a JILA Fellow atomic clocks and other advanced technologies. The from 1974–1986 and 1988–1991, later becoming lab also offers capabilities for micro- and nanofabrica- the Director of the NIST Physical Measurement Laboratory. Credit: NIST tion of custom research devices and advanced imaging systems. The building is intended to support NIST re- search needs for the next 50 years. “My favorite trip was to take people over the Continental Although Gebbie spent most of her career based at Divide and down the Colorado River to Lake Powell and NIST’s current headquarters in Gaithersburg, Maryland, the Grand Canyon. Hard to beat that for scenery. And I she maintained her roots in Boulder. She began her still have a house in Boulder at 7,000 feet with a view in NIST career as a postdoctoral researcher at JILA, NIST’s one direction to the Divide and in the other to Kansas— joint institute with the University of Colorado Boulder. including, of course, the Boulder Airport.” Later, as a lab director, she was responsible for substan- tial programs at NIST Boulder and JILA. The Blodgett in Gebbie’s name recalls her famous aunt, Katharine Burr Blodgett, who invented low-reflectance, “At JILA I learned there is no substitute for talent. Hire invisible glass that is the prototype for coatings used the highest caliber people, provide them the resources today on camera lenses. they need, and let them run,” Gebbie has said. “I never knew any other way of managing.”

She has fond memories of the Boulder Airport, where she learned to fly her mother’s airplane.

Winter 2016 . JILA Light & Matter 8 Atomic & Molecular Physics

The secret to making ultracold KRb molecules inside a 3D optical lattice is create conditions that make it possible to place one atom each of potassium and rubidium on individual lattice sites. Once the atoms are in place, researchers use a change in the magnetic field followed with radiation by a pair of laser beams to form the molecules, which then form communications networks throughout the 3D lattice. Credit: The Jin, Ye, and Rey groups, and Steve Burroughs, JILA A Thousand Splendid Pairs In making ultracold molecules, the courtship is where the action is ILA’s cold molecule collaboration (Jin and Ye Groups with theory support from the Rey Group) recently made a breakthrough in its efforts to use ultracold polar molecules to study the complex Jphysics of large numbers of interacting quantum particles. By closely packing the molecules into a 3D optical lattice (a sort of “crystal of light”), the team was able to create the first “highly degenerate” gas of ultracold molecules. In other words, the ultracold molecular gas was much closer to the lowest possible entropy than ever before. This accomplishment has made it feasible to use the ultracold polar molecules for practical studies of such complicated phenomena as quantum magnetism.

9 Winter 2016 , JILA Light & Matter Atomic & Molecular Physics

Because of its goal of studying complex quantum keep their distance from other atoms, and rubid- phenomena, the collaboration has learned to ium atoms are bosons, which don’t mind a lot of produce ultracold molecules in a 3D optical close contact. Second, potassium and rubidium lattice, which resembles a 3D egg carton of reg- have different masses. Plus they experience the ularly spaced energy wells created by intersect- trap made by light differently. Finally, the potas- ing laser beams. When placed inside the energy sium atoms are hotter than rubidium atoms, and wells in the lattice, individual ultracold molecules harder to cool. With all these differences, it was can “talk loudly” to nearby molecules above and challenging to place just one Rb atom and one K below them as well as to their left and right. There’s atom next to each other in the same well. In fact, it also some weaker communication with molecules turned out it to be best for the K and Rb atoms to farther away. The team’s recent achievement is to completely ignore each other until it was time to fill enough of these energy wells with cold mol- turn them into molecules! This unexpected result ecules to establish a working communications had to be confirmed experimentally and now has network, in which every molecule in the lattice been explained by the Rey theory group. must participate. When it was time to make the molecules, the re- With JILA’s potassium-rubidium (KRb) molecules, searchers used a small change in the magnetic enough turns out to be approximately one KRb field through a Feshbach resonance1 to create molecule for every three or four lattice sites. At such a strong interaction between atoms that they this density, the molecules are able to get well linked up and formed weakly bound molecules. The connected with each other, making it feasible to weakly bound molecules were converted to long- study their complex interacting network. Graduate lived ground-state molecules with a pair of lasers. student Steven Moses and his team from the Jin and Ye collaboration were recently able to create In the end, the researchers succeeded in creating KRb molecules in a large enough fraction of the a thousand splendid KRb molecules, each snugly lattice sites to get the molecules well connected. tucked away in its own lattice site. And, there were enough pairs to establish a communica- To make the molecules inside the lattice, the re- tions network. Now, the Jin and Ye collaboration is searchers had to first place atoms inside the lattice building an improved experimental apparatus that in such a way that many sites contained a single will allow them to see the molecules much more potassium atom and a single rubidium atom. clearly. This new ability to watch the behavior of in- Then, with a small change in the magnetic field, dividual molecules in the lattice will lead to future they turned pairs of atoms into KRb molecules. investigations of communication pathways, spin- However, the first step of getting a pair of different orbit coupling, and other quantum behaviors. atoms into many sites turned out to be the biggest challenge. But, the cold-molecule collaboration 1. A Feshbach resonance is a special magnetic-field strength met the challenge of getting the potassium and where small changes in the magnetic field have dramatic effects rubidium atoms to “like” each other well enough on the interactions of atoms in an ultracold gas. to sit side by side on the same site. Steven A. Moses, Jacob P. Covey, Matthew T. Miecnikowski, Bo Yan, To make them sit peacefully together, the re- Bryce Gadway, , and Deborah S. Jin, Science, 350 659–662 (2015). searchers had to deal with many issues. First, po- A. Safavi-Naini, M. L. Wall, and A. M. Rey, Physical Review A, 92 063416 tassium and rubidium are very different animals, (2015). and as different species, they like different things. Potassium atoms are fermions, which prefer to

Winter 2016 . JILA Light & Matter 10 Just for Fun

Puzzles - It’s all about Chemistry!

Be the first to solve 2 puzzles to win a $25 gift card. The word search answers on the next page can run horizontally, vertically, diagonally and forward or backward.

Turn your correctly-completed puzzle in to Kristin Conrad (room S264) or Julie Phillips (room S211).

11 Winter 2016 , JILA Light & Matter Just for Fun

Winter 2016 . JILA Light & Matter 12 Atomic & Molecular Physics

In an optical lattice, quantum frustration caused by the entanglement (grey shadows) of molecule-like atom pairs and freely moving itinerant atoms (of the same kind) can result in the itinerant atoms appearing to be heavier than they really are. Because the itinerant electrons play the same role as conduction electrons in metals, this behavior may shed light on the conduction properties of magnetic metals. Credit: The Rey group and Steve Burrows, JILA Born of Frustration cientists often use ultracold atoms to study the behavior of atoms and electrons in solids and liquids (a.k.a. condensed matter). Their goal is to uncover microscopic quantum behavior of Sthese condensed matter systems and develop a controlled environment to model materials with new and advanced functionality.

In an exciting new theory investigation, Fellow Ana Maria Rey and research associate Leonid Isaev have showed how ultracold atoms in optical lattices (created with intersecting laser beams) can model the interplay of two fundamental factors affecting the flow of electrons in metals: (1) localized magnetic impurities that behave as tiny magnets and (2) quantum frustration that occurs when the spins of the impurities cannot decide whether to point up or down.

13 Winter 2016 , JILA Light & Matter Atomic & Molecular Physics

When mobile electrons collide with impurities, In an exciting new theory their flow that generates a current is distorted, similarly to how obstacles distort waves in the sea. investigation, Fellow Ana Maria This process is how ordinary metals acquire resis- Rey and research associate tance. However, when the impurities are magnetic and have a permanent magnetic moment, or spin, Leonid Isaev have showed how there is an additional contribution to resistance due to electron collisions accompanied by spin flips. ultracold atoms in optical (This behavior can occur because electrons also lattices can model the interplay have their own spin.) This purely quantum effect profoundly modifies the properties of a metal. For of two fundamental factors instance, to an outside observer, mobile electrons affecting the flow of electrons appear a thousand times heavier that they really are because they tend to spend more time talking in metals. to the local spins and hence move slower. not featureless, however: the same nuclear spins Naturally, the spin-flipping collisions of electrons that enable their creation also give them an inter- depend on how easily the electrons can modify the nal structure with different states encoded by red, state of magnetic impurities. If the local spins are green and blue colors in the figure. rigid and cannot be flipped, the system behaves as an ordinary metal. An especially interesting When an itinerant atom (represented by black situation occurs when this rigidity arises because spheres in the figure) hops into an energy well, it of competing spin-spin interactions with other can rapidly change the state (color) of the bound nearby impurities. Whenever these interactions pair sitting in that well. As itinerant atoms move occur, the magnet is said to be frustrated because a around the lattice they mix the colors of the local magnetic impurity does not know if it should allow molecules, thus making them appear white and en- the mobile electron to flip its spin, or if instead it tangled.1 But at the same time, this process slows should remain rigid, obeying its surrounding lo- down the atoms and makes them appear heavier calized partners. As a result of this confusion, the than they really are, similar to the electrons de- individual spins experience wild quantum fluctua- scribed earlier. Thus, studying a cold-atom system tions. Clearly, magnetic frustration should prevent reveals a peculiar regime in which heavy electrons electrons from efficiently communicating to the (modeled by the freely hopping, but heavy, itiner- local spins, hence making them lighter. But figur- ant atoms) can happily exist in a frustrated mag- ing out which tendency wins remains a puzzle for netic system. scientists. Fortunately, the Ye lab will soon be ready to test Interestingly, observing ultracold alkaline-earth this complex new theory of conduction in the lab- atoms in an optical lattice can shed some light on oratory with ultracold alkaline-earth atoms in an this issue. The ultracold atoms can move and their optical lattice. Stay tuned. nuclei have spins: the former allows scientists to model the flow of conduction electrons, while the 1. When particles are entangled, it means that when something latter can be used to capture the effects of mag- happens to one of them, the other responds. netic frustration by building bound molecule-like states of two atoms and confining them in deep L. Isaev and A. M. Rey, 115, 165302 (2015). energy wells of the lattice. These molecules are

Winter 2016 . JILA Light & Matter 14 Nanoscience

The Land of Enhancement: AFM Spectroscopy Custom AFM cantilevers open the door to watching the process of protein folding/unfolding

he Perkins Group has demonstrated a 50-to-100 times improvement in the time resolution for studying the details of protein folding and unfolding Ton a commercial Atomic Force Microscope (AFM).

This enhanced real time probing of protein folding were initially too curved for use. The team then de- is revealing details in these complex processes veloped an innovative and efficient way to straight- never seen before. This substantial enhancement en out these diving board-like structures, thereby in AFM force spectroscopy may one day have dramatically enhancing the yield of the fabrication powerful clinical applications, including in the process. development of drugs to treat disease caused by misfolded proteins. Misfolded proteins are impli- The new AFM system is optimized for single- cated in such fatal maladies as Creutzfeldt–Jakob molecule force spectroscopy, a technique used disease and mad cow disease, both of which are to mechanically measure the folding and unfold- caused by prions. ing of proteins. The system is capable of detect- ing changes in a protein’s configuration during The Perkins Group has been continually improving the folding or unfolding process because it has AFM as a powerful tool to understand the struc- an amazing resolution in time of less than 1 µs. ture and function of proteins through force spec- The researchers responsible for this feat of nano- troscopy, measuring the tiny changes in forces as engineering included research associates Devin proteins fold and unfold. These folding processes Edwards and Robert Walder, undergraduate stu- lead to protein function. To get better real-time dents Jaevyn Faulk and Matthew Bull (now a grad- force spectroscopy, Devin Edwards made a signifi- uate student at Stanford), Aric Sanders of NIST, cant breakthrough in optimizing AFM cantilevers Marc-Andre LeBlanc and Prof. Marcelo Sousa of for force spectroscopy. The cantilever is the diving- the University of Colorado Boulder, and Fellow board-like structure that pulls on the proteins. Tom Perkins.

The first step for Edwards and his colleagues was The researchers used their new custom AFM to start with very small, commercially available system to monitor the unfolding of a single poly- cantilevers that would respond quickly to changes protein consisting of 59 amino acid subunits. They in protein structure. The key advancement was to found they were able measure the process with substantially reduce the tendency of these small 50–100 times better time resolution than tradition- cantilevers to bounce up and down, or ring, in re- al AFM-based force spectroscopy and see small sponse to normal random movements of the sur- changes better than ever before. The new capabil- rounding liquid molecules (Brownian motion). To ity bodes well for future work in the Perkins Lab. do so, the team used a focused-ion beam micro- fabrication tool to modify specialized cantilevers “We want to watch biological processes like protein that are simultaneously very small (9 mm long) but folding on ever faster time scales,” Perkins said. do not ring. However, these modified cantilevers “Now we can do this more easily (than before) with

15 Winter 2016 , JILA Light & Matter Nanoscience

During AFM spectroscopy of protein unfolding, the 9-µm-long micromachined cantilever (left) custommade in the Perkins Lab significantly reduced the bouncing (ringing) that occurred with a commercially available cantilever (right). Credit: The Perkins group and Steve Burrows, JILA a lot more precision. We are at the point where we the door to other labs adopting the new cantile- can actually watch proteins fold and unfold with ver technology for biological assays, potentially microsecond time resolution.” leading to better understanding of the complex roles protein folding plays in various diseases, and The researchers proved that their new cantile- perhaps leading to new drug treatments. vers work well on a commercial AFM, which can process more samples and work faster than a Devin T. Edwards, Jaevyn K. Faulk, Aric W. Sanders, Matthew S. Bull, custom system. The commercial AFM was retrofit- Robert Walder, Marc-Andre LeBlanc, Marcelo C. Sousa, and Thomas T. Perkins, Nano Letters, 15 7091–7098 (2015). ted with a special small laser detection system with a tiny 3-µm circular spot size that just fit on the tiny reflective gold surface on the top of the cantilever. Using this system on a commercial AFM opens

Winter 2016 . JILA Light & Matter 16 Atomic & Molecular Physics

Natural Born Entanglers

he Regal and Rey groups have come up One of the most interesting parts of this work was with a novel way to generate and prop- that just moving two almost-identical atoms in dif- Tagate quantum entanglement,1 a key ferent spin states on top of one another was suf- feature required for quantum computing. Quantum ficient to cause them to become entangled. When computing requires that bits of information called atoms (which exist as waves in the quantum world) qubits be moved from one get this close together, their location to another, be One of the most interesting waves overlap. As the atom available to interact in pre- waves “talk” to each other, scribed ways, and then be parts of this work was that they discover neither one of isolated for storage or sub- them is staying in one of their sequent interactions. The just moving two almost natural spin states, which group showed that single they are normally happy to neutral atoms carried in tiny identical atoms in different remain in indefinitely. Both traps called optical tweezers spin states on top of one atoms start flipping back and may be a promising technol- forth between spin up and ogy for the job! another was sufficient to spin down. It’s impossible to know which atom is spin up To prove this, the group pre- cause them to become and which one is spin down pared two ultracold neutral entangled. at any give moment. Thus, atoms of rubidium, then the probability of measuring moved them until they were a particular configuration os- on top of one another. This positioning caused the cillates in time. This process leads to entanglement spins of the atoms to become entangled after a bit at certain times. of time. The group then separated the atoms while preserving their entanglement. The researchers “All you have to do is place the atoms on top of one were able to prove the enduring entanglement via another, and they evolve into the state we want,” measurements of the spin states of the separated explained Regal. “You could say it occurs natu- atoms: When one of the atoms was spin up, the rally.” In fact, the process used by the researchers other was always spin down. However, the direc- happens in real materials with identical electrons. tion of each spin fluctuated from one experiment to the next. And, if the researchers then separated the atoms, the atoms stayed entangled. This exciting work was reported online in Nature on November 2, 2015. The researchers respon- 1. When two atoms are entangled, it means the behavior of one sible for it included recently minted Ph.D. Adam atom is correlated with the other. Kaufman, graduate student Brian Lester, research associate Michael Wall, Fellows Ana Maria Rey and A.M. Kaufman, B. J. Lester, M. Foss-Feig, M. L. Wall, A. M. Rey, and Cindy Cindy Regal, and former JILAn Michael Foss-Feig Regal, Nature 527 208–211 (2015). of the Joint Quantum Institute.

17 Winter 2016 , JILA Light & Matter Atomic & Molecular Physics

Placing two rubidium atoms on top of each other results in their naturally evolving into an entangled state. When the atoms are separated, the entanglement is preserved. These characteristics will be important for building a quantum computer. Credit: The Regal group and Steve Burrows, JILA

Winter 2016 . JILA Light & Matter 18 Quantum Information

to the Quantum Drum Song

In the future, quantum microwave networks to manipulate the timing and shape of microwave may handle quantum information transfer via signals while preserving their quantum nature. The optical fibers or microwave cables. The evolu- oscillating drumhead (yellow in the picture) is actu- tion of a quantum microwave network will rely ally part of the microwave circuit’s capacitor, whose on innovative microwave circuits currently being two charge-conducting surfaces are just 40 nm developed and characterized by the Lehnert apart. group. Applications for this innovative technol- ogy could one day include quantum computing, The capacitor’s job is to accumulate and hold elec- converters that transform microwave signals trical charge. The dc electrode (red in the picture) to optical light while preserving any encoded allows the researchers to adjust the capacitor, quantum information, and advanced quantum which in turn allows them to change the circuit’s electronics devices. resonant frequency, making it possible to connect the circuit to other microwave quantum devices. In recent work, the group demonstrated that a flexible aluminum drumhead embedded in ami- The drumhead’s job is to encode the quantum in- crowave circuit made it possible for researchers formation in the microwave signal as mechanical

A false-colored scanning electron micrograph of a circuit under study in the Lehnert lab. The dc electrode (red) makes it possible to adjust the circuit. The capacitor includes a flexible, vibrating drum (yellow) that can store and manipulate microwave signals. This capability could lead to the development of cable- or optical-fiber-based quantum microwave networks capable of using and transmitting separate, mismatched microwave signals. Credit: The Lehnert group and Steve Burrows, JILA

19 Winter 2016 , JILA Light & Matter Quantum Information

motion and store the quantum information intact Microwave Photonics group. The researchers until the drumhead’s mechanical motion can be believe their drumhead-containing capacitor and reconverted back into microwave radiation. After its microwave circuit hold great promise for the reconversion, the researchers verified that the future of quantum electronics. The device may quantum information had indeed come through in allow engineers to build quantum microwave net- good shape. works from separate and even mismatched com- ponents that can be synchronized via the transfer “We’ve learned how to manipulate the information of quantum information in and out of the drum- in a microwave signal in a unique way” explains head. The device could one day make it possible graduate student Adam Reed. “We do this by to prepare quantum states of motion in an object taking the energy in a propagating electrical signal large enough to visible to the naked eye. This and transferring it into a drum that’s vibrating at process would rely on capturing quantum micro- megahertz frequencies even though our electrical wave signals prepared by artificial atoms or su- signal is vibrating at gigahertz frequencies.” perconducting qubits, which are the fundamental units of information in a quantum computer. Reed’s collaborators on this amazing project in- cluded former research associate Reed Andrews, R. W. Andrews, A. P. Reed, K. Cicak, J. D. Teufel, and K. W. Lehnert, Fellow Konrad Lehnert as well as Katarina Cicak Nature Communications 6 10021 (2015). and John Teufel of NIST Boulder’s Advanced

Winter 2016 . JILA Light & Matter 20 In the News In the News

Science Buffs Features JILA’s Innovative In the News Platform for Observing the Ultrafast and Ultrasmall Graduate student Chris Mancuso and senior research A selection of news, awards, and what associate Dan Hickstein of the Kapteyn/Murnane group is happening around JILA recently spoke with Amanda Grennell, a 5th year Ph.D. candidate in Chemistry at the University of Colorado Boulder. The researchers discussed the K/M group’s Jun Ye Selected for 2015 Presidential Rank paper “Strong-field ionization with two-color circu- Award larly polarized laser fields,” which appeared in Physical President Obama has selected JILA Fellow Jun Ye of Review A in March, 2015. The result is a delightful blog NIST’s Quantum Physics Division to receive a 2015 post of the K/M group’s groundbreaking research on Presidential Rank Award. The award cited Ye’s work imaging with circularly polarized laser fields. The story advancing “the frontier of light-matter interaction includes terrific animations prepared by Hickstein. The and focusing on precision measurement, quantum story was posted by the BioFrontiers Science Alliance. physics and ultracold matter, optical frequency me- trology, and ultrafast science.” Enjoy learning about two-color circularly polarized laser fields at http://www.sciencebuffs.org/ The Presidential Rank Awards honor a select group of senior Federal employees for “sustained extraordi- Jan Hall Speaks about Light, Atomic Clocks, nary accomplishment.” These employees are “strong and Testing Einstein’s Assumptions at the Keck leaders, professionals, and scientists who achieve Institute for Space Studies results and consistently demonstrate strength, integ- JILA’s laser guru Jan Hall spoke about light, atomic rity, industry and a relentless commitment to excel- clocks, and testing Einstein’s assumptions on Nov. 4, lence in public service.” 2015, at the Keck Institute for Space Studies. A lively video of the talk can be found at http://kiss.caltech.edu/ Ye was awarded the highest of the two Rank Award new_website/lectures/Hall_Lecture_2015.html levels, the Distinguished Executive, which can be given to no more than 1% of the approximately 6,800 Jan’s abstract is a good synopsis of the video talk: “Even senior Federal employees across the nation. The though this is the 55th year of the laser, progress in its Award includes a monetary prize equal to 35% of the control and application in precision measurements is still employee’s base pay, plus a certificate signed by the accelerating. The optical technology ex- President. ploded in 1999–2000 from the synthesis of advances in independent fields of laser stabilization, ultrafast lasers, The award recognizes Ye as a world leader in laser and nonlinear optical fibers, enabling a thousand-fold and atomic physics. He has a long and diverse list of advance in optical frequency measurement, and search- major accomplishments, including the world’s most es (in the 17th digit) for time-variation of physical “con- accurate , the world’s most stable laser, stants.” Several optical frequency standards now have far extreme ultraviolet frequency combs, major advances better performance than the well-established Cs clock with ultracold molecules and chemistry (partly with that defines time in the SI (metric system) measurement Debbie Jin), pioneering novel quantum many-body system. But adopting a new “atomic clock” to “tick out phenomena, and many other breakthroughs. the seconds” will be daunting in many ways. Current ad- vances in ultraprecise locking are also making possible Congratulations to Jun Ye! stable optical frequencies defined by length and the speed of light, as well as by locking lasers to the resonant

21 Winter 2016 , JILA Light & Matter In the News In the News

frequency of atoms. These two “clocks” represent our Debbie Jin & Jun Ye Highly Cited Researchers current prototypes of the clocks postulated by Einstein for 2015 in 1905 in formulating the Theory of Special Relativity, Deborah Jin and Jun Ye are Highly Cited Researchers which now should be testable into the 18th decimal in a for 2015, according to the Thomas Reuters website. The proposed space-based experiment now being planned website states, “Highly Cited Researchers 2015 repre- by our international Space-Time Asymmetry Research sents some of world’s most influential scientific minds. collaboration (STAR). An improvement in the modulation About three thousand researchers earned this distinc- strategy may allow unexpectedly good frequency-stan- tion by writing the greatest number of reports officially dard performance in a compact device, and so be useful designated by Essential Science Indicators as Highly on earth as well.” Cited Papers—ranking among the top 1% most cited for their subject field and year of publication, earning them Beth Kroger Named 2015 Chancellor’s the mark of exceptional impact.” Employee of the Year Beth Kroger has been selected as a 2015 Chancellor’s Margaret Murnane Named Honorary Doctor Employee of the Year recipient. Kroger, who is JILA’s of Science and Technology at Uppsala Chief of Operations, ensures that JILA is a great place to University do research at the University of Colorado Boulder. She JILA Fellow Margaret Murnane was named an honor- sets an example for JILA staff by viewing her job as an ary doctor of science on September 21, 2015, by the opportunity to learn, be creative, and help the Institute Faculty of Science and Technology at Uppsala University, grow and be successful. Sweden’s oldest institution of higher learning. Murnane was noted in the Uppsala University press release as Kroger serves as JILA’s administrative advisor to Institute being a world-leading expert in ultrafast quantum leadership, oversees staff, and ensures that JILA’s fi- optics. In this field, Murnane is well known for her work nances are balanced and meet ever-evolving internal on high-harmonic generation of laser light that produces and external standards. On top of all this, Kroger keeps an array of beams of laser-like high-energy light ranging JILA running well and makes work fun by providing an from extreme ultraviolet to soft x-ray wavelengths. endless supply of chocolate in her office, weekly treats, and special events such as cookie decorating and paper Murnane co-leads a multidisciplinary team with Henry airplane contests. Kapteyn at JILA and the University of Colorado. The team’s work on laser-like high-energy beams is allow- “I have never met anyone like Beth,” said Kim ing researchers to capture and study the fastest pro- Monteleone, Executive Assistant at JILA, in her nomina- cesses in nature, including the dance of electrons inside tion letter. “She is fair-minded, diplomatic, professional, molecules. wise, polished, brilliant, and open-minded.” Jun Ye’s DARPA Conference Talk Featured in In addition to her duties at JILA, Kroger volunteers Popular Science her time on the University of Colorado Boulder Staff Jun Ye gave a fascinating talk entitled “Let There Be Council, serves on the board of Rotary International, Light (and Thus, Time)” at a DARPA conference on Friday and prepares special meals at the Attention Homes. Sept. 11, 2015 in St. Louis. Ye described how ultrasensi- She volunteers at Greenhouse Scholars (a non-profit tive lasers can measure the very nature of time as well as dedicated to helping low-income, first-generation the ever-changing distance between the Earth and the college students), and is on the Board of Trustees at Moon. Ye’s talk was highlighted the following week in Dakota Wesleyan University. a Sept. 15 article by Rebecca Boyle in Popular Science called “WAIT, WHAT? The most amazing ideas from DARPA’s Tech Conference.”Credit: Steve Burrows, JILA

Winter 2016 . JILA Light & Matter 22 Spotlight

How Did They Get Here? Fellow and Andreas Becker joined the JILA faculty as an Associate Fellow in August of 2008. He became a Fellow in 2012. His specialty is ultrafast laser theory, a topic of interest to several JILA labs, including the Kapteyn/Murnane group. His wife, theorist Agnieszka Jaron-Becker, also arrived in 2008. She is an Associate Fellow of JILA. They are the proud parents of Anna Sophie, who has yet to decide whether she wants to be a physicist when she grows up.

Anna Sophie’s father decided to turn his strong interests in physics and math into a career in physics while still in high school. Soon after starting work at the Universität Bielefeld (Germany), he decided to become a theoretician. He liked interpreting experimental results and making calculations that predict experimental findings, then getting to see the pertinent experiments actually happen a few years later. Becker received his Diploma (equivalent to a Master’s degree) from Bielefeld in 1993 for studies of electron/atom collisions and a Ph.D. from the same institution in 1997 for his work on ultrafast laser theory.

Armed with a Feodor Lynen Research Fellowship from the Alexander von Humboldt Foundation, Becker came to the Université Laval in Quebec, Canada, in 1999 for postdoctoral studies with See Leang Chin. There Chin advised him, “Don’t do only theory. Go into the lab and get your hands dirty.” Becker argued that he’d break everything in the lab and then Chin would have to buy more equipment. Chin retorted, “Don’t worry, all graduate students do this.”

23 Winter 2016 , JILA Light & Matter Spotlight

For 12 months Becker worked with an experimental team studying the effect of intense lasers on the ionization of atoms and molecules and the propagation of ultrashort laser pulses in air and other materials. He not only learned how to gather, read, and interpret data, but also became the first author on the experimental part of a paper that explored both experiment and theory.

In 2001, Becker returned to Germany to obtain his Habilitation, the highest academic qualification one can achieve in Germany. He worked on ultrafast-laser theory both at Bielefeld and at the Max Planck Institute for the Physics of Complex Systems in Dresden. He became head of his own research group in 2002 and completed his Habilitation in June of 2003. Becker worked at Dresden until he and his family came to JILA in 2008.

At JILA, Becker is working on several projects. He is continuing his exploration of the role of Coulomb interactions in the simultaneous removal of two electrons from an atom—a complex topic he has now successfully modeled after more than a decade of work. In collaboration with his wife Agnieszka, he is also studying the use of ultrafast lasers to image electron wave distributions in molecules and deduce the molecular radius of fullerenes (C60–C180). Other theoreticians predict that under an intense laser pulse C60 will breathe—a prediction the Beckers hope can be imaged with their theory and tested experimentally at JILA. Finally, he is exploring the interaction of attosecond laser pulses with electrons in atoms and molecules as well as investigating the control of these dynamics with coherent ultrashort laser pulses.

Becker says he’s excited to be exploring all these ideas here at JILA. “What’s great about being a theorist at JILA is that you can knock, for example, on Henry and Margaret’s door and say, hey I have this crazy idea,” he explains. “Then we can discuss it and hopefully come up with something new.”

Winter 2016 . JILA Light & Matter 24 JILA is a joint institute of the University of Colorado Boulder and the National Institute of Standards and Technology

About JILA

JILA was founded in 1962 as a joint institute of CU-Boulder and NIST. JILA is located at the base of the Rocky Mountains on the CU-Boulder campus in the Duane Physics complex.

JILA’s faculty includes two Nobel laureates, Eric Cornell and John Hall, as well as three John D. and Catherine T. MacArthur Fellows, Margaret Murnane, Deborah Jin, and Ana Maria Rey. JILA’s CU members hold faculty appointments in the Departments of Physics; Chemistry and Biochemistry; and Molecular, Cellular, and Developmental Biology as well as in the School of Engineering. NIST’s Quantum Physics Division members hold adjoint faculty appointments at CU in the same departments.

The wide-ranging interests of our scientists have made JILA one of the nation’s leading research institutes in the physical sciences. They explore some of today’s most challenging and fundamental scientific questions about quantum physics, the design of precision optical and X-ray lasers, the fundamental principles underlying the interaction of light and matter, and processes that have governed the evolution of the Universe for nearly 14 billion years. Research topics range from the small, frigid world governed by the laws of quantum mechanics through the physics of biological and chemical systems to the processes that shape the stars and galaxies. JILA science encompasses seven broad categories: Astrophysics, Atomic & Molecular physics, Biophysics, Chemical physics, Laser Physics, Nanoscience, Precision Measurement, and Quantum Information.

To learn more visit: jila.colorado.edu